The esophagus is a luminal organ that connects the pharynges and the stomach. The major parts thereof are present in the thoracic cavity, and some parts are present in the cervical region and in the abdominal cavity. In the upper portion of the thoracic cavity, the esophagus is located between the trachea and the spine, and it is surrounded by the heart, the aorta, and the lungs in the lower portion. The esophagus delivers food ingested via the mouth to the stomach.
In 2001, the cancer mortality was 238.8 out of 100,000 patients in Japan. The percentages of total deaths accounted for by esophageal cancer have been increasing every year. In fiscal 2001, 5.0% of the male patients who died of cancer died of esophageal cancer, and 1.4% of such female patients died of esophageal cancer. The peak ages for the onset of esophageal cancer are in the 60s to 70s, and males are more likely to develop esophageal cancer. Also, environmental factors such as smoking, drinking, or preference for hot foods are closely related to the development of esophageal cancer. Further, it is known that blood vessels and lymph ducts are abundant in or around the esophageal wall and thus a cancer developed in the esophargus often metastasizes.
Methods for treating esophageal cancer are determined in accordance with the degree of progress (the Japan Esophageal Society (ed.), Clinical Pathology: Rules for Treating Esophageal Cancer, 1999), metastasis, and general medical conditions. The standard method for treating esophageal cancer is described in “Guidelines for Treating Esophageal Cancer” (the Japan Esophageal Society, 2002). At present, the most common treatment method is surgery. The esophagus, including the cancerous portion, and surrounding tissues, including lymph glands, are excised (i.e., lymph node dissection), and thereafter the esophagus is reconstructed using other organs, such as stomach. Surgery, particularly extensive regional lymph node dissection, imposes serious burdens upon patients, and thus, lowered QOL after surgery should be an issue of concern. The early-stage cancer that remains in the mucosa may be occasionally treated by endoscopic demucosation. Also, radiation therapy may be occasionally carried out for both radical cures and symptomatic therapy. Further, chemotherapy may be carried out in combination with surgery or radiation therapy. At present, use of 5-fluorouracil in combination with cisplatin is considered to be the most effective chemotherapy.
Esophageal cancer is often found by consultation with a patient who has noticed symptoms, such as discomfort while swallowing, swallowing difficulty, retrosternal pain, or chest discomfort. These symptoms, however, occur as a result of the growth of cancer in the esophagus, and the cancer, which is found at the time of consultation following self-examination, has already progressed or metastasized outside the esophageal wall, and such a cancer often indicates a poor prognosis.
Esophageal cancer is definitely diagnosed by the imaging test, endoscopy, and biopsy in the esophargus. Biopsy specimens are collected at the time of endoscopy or surgery, pathological specimens are prepared, and the diagnosis is made on the basis of the histopathological classification. Accordingly, there is a demand on development of a simple, rapid diagnosis technique that can predict the presence or absence of esophageal cancer based on the properties of cells obtained by endoscopy.
Until now, the molecular-biological diagnosis technique that involves the use of markers contained specifically in esophageal cancer tissues has been proposed, and this technique can rapidly produce objective results and assist rapid diagnosis.
As the markers for clinical diagnosis of esophageal cancer, serum protein markers, such as SCC, CYFRA21-1, and CEA, have been used so far. Besides them, proteins as described in JP Patent Publication (kokai) No. 2003-259872 A and JP Patent Publication (kohyo) No. 2000-511536 A have also been reported. However, these markers have poor sensitivity and specificity, and the sensitivity of CYFRA21-1, which is likely to have the highest sensitivity, is as low as about 33.9% (Nakamura, T. et al., 1998, Diseases of the Esophagus, vol. 11, pp. 35-39) to about 43.9% (Kawaguchi, H. et. al., 2000, Cancer, vol. 89, pp. 1413-1417). Thus, this technique has not yet enabled to determine the presence or absence of esophageal cancer cells by detecting the serum markers alone or in combination.
As another marker that utilizes genes for specifically determining whether or not a biopsy sample from a subject contains esophageal cancer cells, use of chromosome aberration (see, for example, JP Patent Publication (kokai) No. 2001-17200 A and JP Patent Publication (kokai) No. 2002-272497 A) and epigenetic sequences of genes (e.g., JP Patent Publication (kohyo) No. 2004-505612 A) has been disclosed. Also, a plurality of results of the exhaustive analysis of gene expression using a DNA chip have been reported (see, for example, WO 2006/118308; Luo, A. et al., 2004, Oncogene, vol. 23, pp. 1291-1299; Zhi, H. et al., 2003, International Journal of Cancer, vol. 106, pp. 327-333; Lu, J. et al., 2001, International Journal of Cancer, vol. 91, pp. 288-294; Kazemi-Noureini, S. et al., 2004, World Journal of Gastroenterology, vol. 10, pp. 1716-1721; Xu, S. H. et al., 2003, World Journal of Gastroenterology, vol. 9, pp. 417-422; and Su, H. et al., 2003, Cancer Research, vol. 63, pp. 3872-3876). WO 2006/118308, in particular, provides 20 types of genes that determine the presence or absence of esophageal cancer cells by performing detection techniques in combination. In this technique, however, whether or not the samples contain esophageal cancer cells is determined with the use of different machines, which complicates the diagnosis. When one of the machines predicts that the sample contains esophagal cancer cells but the other machine predicts that the sample dose not contain esophageal cancer cells, also, diagnosis may occasionally become impossible. Furthermore, examples of the reported markers that utilize a single gene expression as an indicator include: the SPRR3 gene (Small proline-rich protein 3) as described in WO 2003/042661, Chen, B. S. et al., 2000, Carcinogenesis, vol. 21, pp. 2147-2150, and Abraham, J. M. et al., 1996, Cell Growth & Differentiation, vol. 7, pp. 855-860, the fgf3 gene as described in Kitagawa, Y. et al., 1991, Cancer Research, vol. 51, pp. 1504-1508, the CSTB gene (cystatin B, liver thiol proteinase inhibitor) as described in Xu, S. H. et al., 2003, World Journal of Gastroenterology, vol. 9, pp. 417-422 and Shiraishi, T. et al., 1998, International Journal of Cancer, vol. 79, pp. 175-178, the UCP2 gene (mitochondrial uncoupling protein 2) and the COL3A1 gene (3′ region for pro-alpha(III) collagen) as described in WO 2003/076594; the UPK1A gene (uroplakin 1A) as described in WO 2003/042661; and the HSPA1B gene (heat shock 70 kDa protein 1) as described in Kawanishi, K. et al., 1999, Cancer, vol. 85, pp. 1649-1657. As markers for epithelial malignant tumors, the RRM1 gene (ribonucleotide reductase M1 polypeptide) and the like as disclosed in WO 2006/119464 are known. However, use thereof is not sufficient for the diagnosis of the presence or absence of esophageal cancer.